TCP/IP (Transmission Control Protocol/Internet Protocol) is the transport mechanism underlying the Internet. It is also the underlying protocol for many intranets and business applications in existence today. TCP/IP was started as an educational and scientific network. It was not designed to handle high-volume traffic with the requirement of availability 7 days per week, 24 hours per day. TCP/IP was designed primarily as a fast transport mechanism. Because of this design point, there were few backup or redundancy measures incorporated into TCP/IP.
Through the growth of the Internet, which includes the world wide web, requirements have arisen for higher availability and greater reliability for host TCP/IP networks. This has become especially true where the TCP/IP host controls business applications or transactions. The design of TCP/IP is such that each physical network interface adapter has associated with it an address. This address is unique within the entire network and is the method by which all other devices communicate with the adapter or the devices connected through the adapter. If a given TCP/IP host has multiple interface adapters, the users communicating with the host must select an interface adapter which they chose to use. The user must then reference the host by the address of the particular adapter which the user has chosen to use.
The above method works well when each host has one interface adapter or where the interface adapters never fail, but in large host systems where there are more than one interface adapter available, situations arise where one of the interface adapters fails. When this happens, under the current TCP/IP implementations, the information that is being sent to the failing interface adapter is incapable of being rerouted to the functioning interface adapter(s). The only method available to rectify the break in the communications link is to either replace the failing adapter and configure the new adapter with the same network address as the adapter that failed or to modify the application sending information to send information to the new network adapter, or to detect the failure, determine which resources are affected and broadcast the new location upon which the affected resources can be found. All of these potential solutions require the intervention of an operator or an applications programmer which will result in the loss of packets and the disruption of traffic.